Preliminary Technical Data
UG-1828
Rev. PrC | Page 263 of 338
Figure 253. 1.8 V Transmitter Power Supply Routing on the ADRV9001 Evaluation Board
An example of the balun feed supply designed to achieve the isolation managed in the evaluation board is shown in Figure 254 and Figure
246.
DC Balun
When a Tx balun that is able to conduct dc is used then the system shown in Figure 254 should be used. The decoupling cap near the Tx
balun should be placed as close as possible to the balun’s DC feed pin. Its orientation should be perpendicular to the ADRV9001 device so
the return current avoids a ground loop with the ground pins surrounding the Rx input. The customer card provides an option to install
an RF isolation inductor which can provide extra isolation between the Tx1 and Tx2 balun supply feeds. A 10µF capacitor and a 0.1 µF
capacitor are helpful on the dc feed pin to eliminate Tx spectrum spurs and dampen the transients. Note that when this supply approach
is used the series matching components must be dc shorts. It is recommended to use 0 Ω if an inductor is not needed to match the balun
impedance to the Tx output impedance.
Figure 254. Transmitter Power Supply for a Balun with a Center Tap
Chokes
The ADRV9001 evaluation board provides flexibility to be configured to use a Tx balun that is not capable of conducting dc current. In
such a scenario, the user should install dc chokes as well as their decoupling capacitors as highlighted in Figure 255. Care should be taken
to match both chokes to avoid potential current spikes. Difference in parameters between both chokes can cause unwanted emission at Tx
outputs. Note that if the differential input to the balun can create a dc short to ground (through the balun), the series matching
components must be capacitors. If a short can form on the single-ended side, the single-end series blocking element must be a capacitor.
1.8V COMMON
POWER PLAIN FEED
1.8V COMMON
POWER PLAIN FEED
TX2 SUPPLY DOMAIN
(VANA2_1P8)
TX2 SUPPLY DOMAIN
(VANA1_1P8)
LOOP BETWEEN CENTRE TAP BALUN /
EXTERNAL CHOKES AND TX POWER
DOMAINS NEEDS TO BE KEPT SHORT.
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DC FEED FROM
VANA1/2_1P8 PLANE
RESERVOIR
CAPACITORS
OPTIONAL RF
ISOLATION INDUCTOR
BALUN
RF BALUN SELECTION COMPONENTS.
DC CONTINUITY ON DIFFERENTIAL SIDE
DECOUPLING
CAPACITOR
(ORIENTATION IS
IMPORTANT)
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